Contour activating device

ABSTRACT

A rotatable activating device for contacting and activating a contoured surface during the electrodeposition thereon of a metal coating. The device has an outer surface composed of a nonconductive, porous, compressible, fluid-entrapping and circulating, fixed hard particle-supporting media contoured to complement the contours of the surface to be activated and an internal complete or partial core of a conductive material.

Umted States Patent Eisner 1 Dec. 19, 1972 I54] CONTOUR ACTIVATINGDEVICE FOREIGN PATENTS OR APPLICATIONS [72] In Steve Eisner,Schenectady, N 18,643 1899 Great Britain ..204/DIG. 10 [73] ssig e zNorton Company, Troy, N Y. 493,108 9/l938 Great Britain ..204/DIG. 10[22] Filed: March 26, 1971 Primary Examiner-John H. Mack I AssistantExaminerRegan J. Fay [2]] Appl- N05 1281240 Attorney-Hugh E. Smith andHerbert L. Gatewood [52] 11.5. C1 ..204/217, 204/224 R, 204/271, [57]ABSTRACT 204/DIG. l0 A rotatable activating device for contacting and ac[51] Int. Cl. ...B23p l/00 tivating a contoured rf ring he elecrodeposi- [58] Field of search....;...204/217,D10. 10, 224, 271 tionthereon of a metal coating- The device has an outer surface composed ofa non-conductive, porous, [56] References Cited compressiblef'luid-entrapping and circulating, fixed' hard particle-supporting mediacontoured to comple- UNITED STATES PATENTS ment the contours of thesurface to be activated and an internal complete or partial core of aconductive 3,619,401 11/1971 Eisner ..204/D1Gv 10 materiaL 3.6l6,289lO/l97l Ellis ..2()4/2l7 i 1,214,271 1/1917 Bugbee ..204/D[G. 10 5Claims, 9 Drawing Figures SHEET 1 BF 2 PATENTEDME 19 mm Inventor SteveEisner W wk UNIT" 7 u A r /H mmk His Afforney.

sum 2 or 2 PATENTED DEC 19 1912 II 11/ I CONTOUR ACTIVATING DEVICERELATED APPLICATIONS This application represents a specific embodimentof the porous-activating media disclosed and/or claimed in one or moreof my copending U.S. Applications Ser. No. 34,500 filed May 4, 1970, nowU.S. Pat. No. 3,619,384; Ser. No. 863,509, filed Oct. 3, 1969, now U.S.Pat. No. 3,619,389; and Ser. No. 863,499, filed Oct. 3,1969, now U.S.Pat. No. 3,619,401.

FIELD OF THE INVENTION The present product, although resembling an abravsive product, is specifically designed to provide essentially no stockremoval in use. This seemingly contradictory statement stems from aprocess discovery as described and claimed in theaforementionedapplication, Ser. No. 34,500 of Steve Eisner, filed May 4,1970, now U.S. Pat. No. 3,619,384. As related therein, the use ofproducts of the general type to which that of the present inventionbelongs to lightly and repetitively contact a surface (an electrodepositsurface in the cited application) results in an activation of thesurface making possible speeds of electrodeposition far above thoseindicated as achievable by the prior art. In particular, the presentdevice relates to that portion of the electrodeposition field whereinthe surface to receive the deposit may be other than flat and smooth andhence a problem of obtaining uniform current density exists.

The present device is designed for use in a process in which the currentdensity is high compared with that of conventional processes and inwhich the surface of the deposit is repetitively contacted at extremelyshort time intervals by what is termed herein as dynamically hardparticles. By this term is meant that the combination of the hardness ofthe particles, the contact pressure of the particles on the surface ofthe electrodeposit and the speed at which such particles are movingrelative to the electrodeposit surface is such as to produce an actionon such surface sufficient to mechanically activate'? the surface.Activating the surface of the electrodeposit as the term is usedherein'requires the generation of new surface defect sites throughmechanically distorting the crystal lattice of the metal deposited. Itis believed that the mechanism is rather complex and consists of severalactions taking place essentially simultaneously. First, there is the newsurface defect site generation resulting from distortion of the crystallattice structure as mentioned above. This provides growth sites formany more asperities than would be the case absent this mechanicaldistortion. Additionally, any dominant asperities already formed are cutoff or bent over and crushed by the dynamically hard particle contact.These two actions result in substantial elimination of the currentrobbing which takes place at the asperities formed in normal plating andis believed to be one of the major contributing factors to the abilityto maintain high current densities for substantial periods of time whilemaintaining acceptable deposits with this process. Further, the actionof the activating medium is believed to result in the removal orsubstantial diminution of the stagnant polarization layer overlying theelectrodeposit surface and to maintain a high concentration of metalions adjacent such surface due to the pumping action of the activatingmedium which carries a supply of fresh electrolyte across theelectrodeposit surface at a high flow rate.

The device utilized in this process consists of a surface disturbing oractivating medium having the characteristics of providing a plurality ofsmall, dynamically hard, relatively inflexible, non-conductive particlesheld in substantially fixed, spaced relationship to one another andgenerally vertical to the surface receiving the deposit by a preferablyporous, compressible, fluid-entrapping and circulating matrix orsupporting member. Further, relative motion is provided during thedeposition operation between the surface receiving the deposit and theactivating medium.

7 In addition, sufficient pressure is applied to said activating mediumin a direction normal to the electrodeposit surface to causemechanicaldistortion of the crystal lattice structure of the metal depositedthereon. The spacing of the particles and the speed of relative movementis such that the deposited metal surface above any given point on thecathode surface is contacted or influenced by a particle at extremelyshort time intervals, e.g. intervals in the range of 6.1 X 10- to 3.8 X10' seconds. Fresh electrolyte is supplied to the zones of activatedmetal deposit at a high rate through entrapment by the porous,fluid-entrapping and circulating activating medium.

Where the surface to be plated (the cathode surface) is not flat andsmooth, i.e., has convex and concave contours, the problem becomescomplicated due to variations in current density resulting from unevendistances from a fixed anode system. The device of the present inventionis directed primarily to this type of surface plating. Another problemencountered is that seldom can one single device he contoured to fit allof the contours of a complex workpiece. This requires the use ofmultiple devices according to the present invention in order to coverthe entire surface of the workpiece and imposes the additional problemof covering adjacent areas with plate from different operations withoutleaving parting lines or lines of demarcation between the plates laiddown at different times or by different devices.

DESCRIPTION OF THE PRIOR ART Abrasive products have historically been soconstructed as to maximize the cut or abrading potential of the specificconstruction concerned. In the present instance the opposite is true.Spaced particles are essential, but they must be so positioned in theproduct as to provide a minimum of abrasion in use. The closest type ofproduct to that described herein, we believe, has been the brush orcloth used in so-called brushplating. This, however, does not containthe spaced particles required in the present structure.

SUMMARY The device of the present invention is a rotatable formed wheelor drum having an outer surface of a porous, compressible,non-conductive hard particlesupporting media which is capable ofentrapping and circulating fluid with which it comes into contact. Thedistance from the axis of the drum to the outermost portion of suchsurface may be uniform throughout the drum length or it may vary oversuch length. The device will be tailored for the particular surface uponwhich it is to be used and will be formed into a complementary profileof such surface.

l060ll 0285 lnwardly spaced from the outer surface is an inert,conductive anode means. The anode means may underliethe entire outersurface or it may underlie only a portion thereofFurther, the anodemeans may be a unitary member or it may be made up of a plurality ofmembers, e.g. discs.

Electrical contact between the anode means and from the anode means toground is achieved through the shaft which extends along the axis ofrotation of the device.

DRAWINGS FIG. 1 is a perspective view of one form of the device of thepresent invention.

FIG. 2 is a sectional view of the device of FIG. 1 along the line A-A.

FIG. 3 is a partial plan view of a modification of the device ofthepresent invention.

FIG. 4 is a sectional plan view of still another type of deviceaccording to this invention.

FIG. 5 illustrates in a cross-sectional view the anode arrangement foroverlap plating.

FIG. 6 illustrates in cross section another form of the present device.I

FIG. 7 is a schematic view showing a device of the present invention asapplied to a complex contour surface.

FIG. 7-A shows another portion of the surface shown in FIG. 7 beingplated so as to overlap the portion plated in FIG. 7.

FIG. 8 illustrates the use of a device according to the presentinvention using a flood of electrolyte instead of an immersed system.

DESCRIPTION OF PREFERRED EMBODIMENTS The device of the present inventionprovides for the controlled application under pressure, both normal toand parallel with the electrodeposit surface, of a supporting,preferably porous and compressible, non-conductive, fluid-entrapping andcirculating matrix which supports on its surface in closely-spaced,fixed'relationship a plurality of small, relatively inflexiblenon-conductive particles. These particles are so positioned in and onthe matrix as to contact the deposit forming on 'As described above, theelectrodeposit surface is activated by multiplying many times the numberof nucleation sites on such surface and generating a controlled growthof a tremendous number of very short asperities which are repetitivelyrestricted in vertical growth throughout the deposition cycle. The metaldeposit reflects this action since photomicrographs of the crosssections of such deposits illustrate a structure in which the growthaxis of the crystals appears substantially parallel to the substraterather than showing the normal columnar vertical orientation ofconventional electrodeposits.

This technique has been found to increase the limiting currentdensitymany times beyond that possible with other methods, resulting in muchmore rapid metal deposition than is possible with such other methods andhas further been found to produce a hard, dense, smooth metal deposit.These results are achieved even through there may be minor metal removalfrom .the' deposit on the cathode surface, cutting down slightly thetotal thickness of such deposit. This metal removal is minimized bycontrol of the pressure applied to the activating medium but in order toinsure adequate activation of the surface it is necessary to applysufficient pressure to produce a light scratch patternin the metaldeposit. Thus the dynamic hardness of the particles may be substantiallygreater than the actual hardness, e.g. a resin particle may produce ascratch in a much harder nickel deposit. This scratch pattern may bevisible to the naked eye but, in any case, will be seen under amagnification of 10,000 power or less. While the scratches may beproduced by metal removal, preferably the dynamic hardness is socontrolled that a displacement of metal atoms on the surface rather thanactual removal is the basis for the scratch formation.

By using small, relatively inflexible, non-conductive particles as theactivating tool, no spot on the deposit surface is covered for anyappreciable length of time by the activating particle. Further, sincethe activating particles are fixed to the supporting matrix, there is nodanger of a particle being occluded as a crack-initiating impurity inthe electrodeposit. These particles are generally randomly distributedover at least the external surface of the matrix and are preferablyspaced in fixed relation to one another over very short spans, e.g. 1.25X 10" inches to 5.65. X 20' inches. If desired, accurate and non-randomdistribution-of the particles on the supporting matrix can be resortedto although this is generally an unnecessary complication. By the termparticle as is used herein is meant not only completely separate anddiscrete three-dimensional bodies, but also larger bodies with aplurality of points, tips, projections or the like thereon as forinstance a relatively hard resinous coating on a fiber wherein thecoating contains multiple irregular spaced projections and is generallyuneven in nature. The particles, as described herein, contact or atleast influence essentially all of the surface of the electrodeposit andare believed to knock down or cut off as they form most of the dominantasperities on such surface. The particles themselves may vary widely insize from I X 10" inches to 1.25 X 10" inches (average diameter) forexample, but should generally be in the size range of from 9 X 10"inches to 2 X 10" inches for best results. The particles can generallybe defined as hard, i.e., having a Knoop hardness in excess of 10.0, butthe degree of hardness per se is not critical except that control shouldbe exercised not to use a product which is too abrasive for theparticular metal being deposited. The degree of pressure applied mustalso be considered with respect to the hardness of the particles andgenerally with the softer range of particles more pressure normal to thecathode surface is required than with the harder range of particles.

l060ll 0286 As indicated above, the controlling factor is the dynamichardness of the particles, i.e., the apparent hardness resulting from acombination of the actual Knoop hardness, the pressure applied and thespeed with which the particles are moved across the electrodeposit. Avisible indication that the dynamic hardness is sufficiently high is thepresence in the deposit of the scratches visible under 10,000Xmagnification.

The matrix used to support the activating particles is preferablyelectrolyte-permeable, having a through porosity in the order of atleast 6.5 Sheffield units (as measured by a Sheffield porosimeter usinga 2% inch ring). Preferably, this matrix is also at least somewhatcompressible and deformable so that it can be conformed to irregularsurfaced cathodes and'associated deposits where necessary.

In the device of the present invention, the porous, particle-supportingmedia described above is formed into a wheel or drum. This may takeseveral forms as is more fully described below, but in each instance, atleast the outer surface of the drum is formed of this type of media. Insome instances the outer surface may be provided in the form of a sheathsurrounding or superposed over a central core. In other instances theouter surface may be formed by discs of the porous media positionedaround and extending outwardly from the shaft upon which the device isrotated in use.

Underlying the outer surface over at least aportion of the length of thedrum is an inert, conductive anode material. The distance from the outerportion of this anode material to the outer surface of the overlyingporous, particle-supporting media is preferably substantially the sameat all points along the length of the drum in those portions where theanode material is present.

The anode material used in the device of this invention is preferablylead. This is easy to form, inert to most electrolytes which aredesirable for use and has the desired conductivity. Preferably theelectrolyte to be used with this device is of the sulfate type. Thiscauses a minimum problem with respect to corrosion and fumes and is lesstoxic than most other systems. The porous media may be of the non-wovenvariety, described in the aforementioned copending applications, and maybe needle-punched for increased strength if desired. So long as theporosity and resistance to the chemical action of the electrolyte ismet, any non-woven media may be used for the support. Woven materialsmay also be used if desired and any of a variety of weaves, sateen,leno, square, etc., can be utilized. The principle function of thesupporting media is to provide a cushioned or resilient support for thehard particles with the secondary function of entrapping and circulatingor pumping fresh electrolyte into the plating zone. As illustratedbelow, brush materials can be utilized with the hard particles anchoredon or in the bristles.

Referring now to the drawings, FIGS. 1 and 2 illustrate one type ofdevice embodying the present invention. A drum having a concave portion11 is provided with an outer sheath of a non-conductive, porousparticle-supporting media 12 having a plurality of spaced particles 13affixed thereto. Internal of the outer sheath 12 is a correspondinglayer of inert anode material 14. The anode material 14 is supportedfrom a centrally-disposed hollow hub member 15 by a plurality of supportmembers 16. I-Iub member 15 is adapted to slip over and fasten rotatablyto a drive shaft 17 which is connected to the positive pole of a DC.source as shown at 18. Keys 19 are used to connect shaft 17 to hub 15and electrical conductivity is maintained from the shaft 17 through hub15 and support members 16 to the anode layer 14.

FIG. 3 illustrates another type of device embodying the presentinvention. Here a plurality of discs 20 of the porous non-conductiveparticle-supporting media are provided affixed to a rotatable shaft 21.Again, a plurality of spaced particles 22 are affixed to at least thesurfaces of the discs 20. Interleaved between discs 20 on shaft 21 are aplurality of inert anode discs 23, likewise mounted for rotation onshaft 21. For purposes of illustration, the discs 23 are shown asproviding definite demarcation areas between the outer ends of discs 20.In actual construction, the discs 20 are usually sufficiently uneven andcompressibly resilient that the outer ends of discs 20 will form asubstantially unbroken surface and anode discs23 will be completelyhidden. Again, shaft 21 is designed to be electrically grounded and toin turn ground the anode discs 23.

FIG. 4 illustrates the use of bristles 40 having spaced 7 hard particles41 affixed to the outer ends thereof. Here, as in FIG. 3, a plurality ofinert anode discs 42 are provided, mounted for rotation on shaft 43which acts also to electrically connect the anode discs 42 to thepositive pole of a DC. source. Bristles 40 are shown as mounted at theirinner ends in resin blocks 44 affixed to shaft 43. As illustrated, theanode discs 42 and bristles 40 vary in length to provide a contoursurface for the device. It will be noted here, as in FIGS. l-3, that thedistance'between the outer surface of the particle-supporting media 40and outer ends of the anode discs 42 remains substantially the same overthe entire length of the device regardless of the variation in distancebetween such outerv surface-and the shaft 43. As mentioned in connectionwith FIG. 3, the particlesupporting media tends to hide the presence ofthe anode discs and the characteristic is illustrated in this drawing.

FIG. 5 illustrates an anode to outer surface configuration which is usedto minimize problems where overlapping plate is to be deposited. As willbe more clearly shown in FIGS. 7 and 7-A, it is frequently necessary, inorder to cover all the contours of a'multi-contoured article, to utilizetwo or more formed devices according to the present invention. The bestway to accomplish this is to ensure that the edges of the deposit laiddown beyond or immediately adjacent the end of an activating device,such as those illustrated herein, are not burnt. By keeping the currentdensity at the ends of the activator low enough to prevent any burntelectrodeposit growth at such ends, a tapered plate is deposited underthe activator. When the next device overlaps to apply plate to the nextsection of the workpiece, the plate goes down without leaving anynoticeable line of demarcation. This current density gradient isobtained by spacing the anode from the ends of the device as isillustrated in FIG. 5. Here, in contrast to the alternate anodedisc-porous media disc construction of FIG. 3, a unit is shown with asingle anode disc 50 mounted on shaft 51 which again is connected to thel060ll 0287 positive pole of a D.C. source. Multiple porous media discs52 carrying spaced particles 53 are mounted on each side of anode disc50 as shown. The current density at the outer ends 54 of the last discs52 will be low enough to prevent burning and to prevent overlap of theplate deposited. 1

FIG. 6 illustrates a cross section of another device somewhat similar tothat of FIG. 1 in that a sheath or covering 60 of porousparticle-supporting media is provided having a plurality of spacedparticles 61 thereon. In this instance, the anode 62 forms a shellinside the cover 60 and is adapted to fasten at one end to a drive shaft63 by means of bushing 64. Shaft 63 is electrically connected to thepositive pole of a D.C. source.

FIGS. 7 and 7-A illustrate the application of a device of the presentinvention to a complex shape and further illustrate the overlap platingmentioned above. Here a plating bath 70 is provided in a suitable tank71. Mounted within the plating bath 70 is a contoured workpiece 72 whichis to be plated. As shown, this is supported by members 73 and 74 in afixed relationship to tank 71. Workpiece '72 is electrically connected,as schematically shown at 75, to'act as a cathode in the bath 70 and, inorder to prevent immersion plating, has previously been given a strikeor thin, conventionally-electrodeposited metal film. This use of astrike is required when the contoured part is to be plated immersed asshown in FIGS. 7 and 7-A. In FIG. 7, a formed wheel 76 mounted on driveshaft 77 which is connected to the positive pole of a D.C. source isshown. As in the previous illustrations, the outer surface of wheel 76is composed of a porous media supporting spaced particles thereon. Wheel76 contacts a portion of one end only of workpiece 72 as shown. Theanodic center of wheel 76 is illustrated in dashed lines at 78. As thewheel 76 rotates under the drive of shaft 77 from a suitable drivingsource such as an electric motor (not shown) the surface of workpiece 72in contact with wheel 76 receives an electrodeposit at a high rate ofspeed. Due to the configuration of the anode 78, that portion of theworkpiece 72 designated as X. in the drawing will receive a plate whichthins out as the outer edge of the wheel is reached. In FIG. 7-A, thesame workpiece 72 is now being plated over an adjacent section by wheel80. Here the anode center 81 tapers slightly, as illustrated, to keep acurrent density gradient going from a minimum at the wheel end 82 to amaximum just beyond the portion X" of workpiece 72. Wheel 80 is rotatedby shaft 83 which is also mounted for lateral oscillation as shown bythe arrows. The plate which is now deposited on portion X complementsthe plate deposited thereon in the illustration of FIG. 7 and gives auniform structure of equal thickness to that elsewhere depositedunderthe activating wheels 76 and 80. I

FIG. 8 illustrates another manner of using the devices of the presentinvention in a plating operation. Here a formed wheel 90, againconsisting of the type of construction previously described, is rotatedby ground shaft 91 against a portion of the surface of a cathodicworkpiece 92. Here, however, workpiece 92 is not immersed in a platingbath but the electrolyte 93 is supplied by high pressure jets 94 and 95directly into the interface between wheel 90 and workpiece 92. Excesselectrolyte 93 is collected in the bottom 96 of a suitable container 97and recirculated as at 98 for re-use. In this type of system, apreliminary strike on the workpiece 92 is not required although it maybe used if desired.

Although, as indicated above, a variety of structures embodying thepresent invention are available, the method of formation of the devicesof this invention is common to all up to apoint. In all instances it isdesirable to first prepare a line drawing of the contour surface to-beplated. This can conveniently be-done either from a drawing of the partto be plated if one is available, or directly from the part using acontour or profile gage. This is an assemblage of flat plates, usuallyaluminum, and quite commonly of about one-sixteenth inch thickness perplate. The plurality of plates is slideably mounted on one or more rodsso that the vertical distance of any one plate can be altered withrespect to that of any other plate. Suitable clamping means are providedin these conventional devices to hold the plates in any desiredrelationship. The assembly of plates is applied to the contour to beplated and the gage is adjusted so that the contour is defined by theedges of the plates. The plates are then clamped in this position and aline is drawn on a sheet of paper connecting each edge of the platesthus giving a reproduction of the contour on the paper. A second lineparallel to this contour line is then drawn at a short distance from thefirst line. This distance, which will be the distance between theoutside edge of the anode and the outside surface of the porousparticle-supporting media in the finished drum, can be varied withinquite wide limits, i.e., from about one-sixteenth inch or less to asmuch 4 inch or more. Generally it is desired to maintain this distanceas short as possible in order to minimize the IR drop between the anodeand the contoured workpiece cathode. The minimum distance is set by thedistance at which short circuiting becomes a problem and this will becontrolled somewhat by the type of porous surface media used in terms ofits compressibility and wearability. Also, the amount of movementpermitted by the work-mounting fixture and the drive spindle of thedevice must be considered. The

preferred distance between the anode and the outer.

surface of the porous media ranges from one-sixteenth to 1 inchalthough, as indicated above, greater and lesser spacings are operable.Oncethese two lines are established, they can be used to lay out thedesign for the drum or wheel. A base line is drawn to represent the axisof rotation and lines are drawn normal to such base line at each end ofthe portion of the contour it is desired to reproduce in wheel form.This then represents a plan view of one half of the wheel to be formed.If spaced discs are to be used, the width of the discs and the anodespacers is determined and then lines are drawn to represent these. Thedistance from the base line to the nearest contour line is the radius ofthe anodes while the distance to the farther of the contour line fromthe base line isthe radius of the porous media discs. If a sheath-typewheel is to be made, the anode can be formed using the contour drawingfor measurement of proper dimensions. For the disc-type structure, acenter hole is provided in each disc dependent upon the size of shaftupon which they are to be mounted.

As a simple example of this type of device, a formed wheel was made upof alternate lead anode discs and porous non-woven material discs. Theanode discs were one-sixteenth inch thick while the porous non-woven wasapproximately one-fourth inch thick. A profile was made of a contourconsisting of the arc of a 1% inch circle. The chord of the arc was 1%inch. Using a profile gage, this contour was transferred to a sheet ofpaper and the measurements from an arbitrarily drawn base line gave thefollowing dimensions for the porous discs (reading from left to right asthe discs were to be assembled:

Disc

1. 1% to 1% inch(l% inch) 2. 1% to 1-7/16 inch (1-7/16 inch) 3. 1% to1-% inch (1% inch) 4. 1% to 1-7/16 inch 1-7/16 inch) Rather than toexactly match the contour, the longer radius was used in each instanceas indicated in the parenthesis. The anode discs which go between eachof the porous discs were then measured from the diagram with A being theanode disc between discs 1 and 2 above, etc.: 7

Anode Disc A l-1/16-l% inch (1% inch) B 1-3/16-1% inch (1%1 inch) C 1%-1% inch (1% inch) D l-3/16 inch-1% inch 1% inch) Again, the longerradius for each disc was used as indicated in the parenthesis. Twoadditional lead discs, treated with stop-off lacquer (conventionalplating technique) of 1 inch radius were used outside discs 1- and 5.The discs were then assembled on a inch diameter steel shaft havingthreaded ends and a nut was threaded up against each outside lead discto hold the assembly in position. The make-up of the wheel, using thenumerical designations above was:

1 inch lead disc-lA-2-B3-C4D -5-l inch lead disc The formed wheel wasthen mounted in a drill chuck affixed to an electric motor and rotatedat a speed of 250-300 RPM. The contour part was immersed in a roomtemperature, brightener-free zinc pyrophosphate plating bath andconnected to a source of negative potential. The wheel was then rotatedagainst the contour surface for one minute and plate was deposited at acurrent density of 1,200 amps/ftF. A uniform bright zinc plate plate wasdeposited in the area under the wheel. 1n the adjacent areas of thecontour outside that covered by the wheel, the deposit was dull andburnt.

For many types of decorative plate, the exacting procedure outlinedabove is not required. It will usually be used in forming a wheel ordrum using a cover sheath over a shaped anode but may often be dispensedwith in the case of the ganged disc construction. For example, using thesame contoured workpiece described above, a porous wheel was made upusing the same non-woven, particle-supporting media as was used in theabove example. Here the discs were all 4 inches in diameter and wereroughly trimmed on the outside surface of the desired curvature. Fivenon-woven discs, each about one-fourth inch thick were assembled on ainch diameter steel shaft alternating with l/l6 inch thick lead washers.In this instance, no attempt was made to match the contour of thewashers with the outer surface contour and all six of the lead discswere 2% inch in diameter. The outer lead discs were again treated withstop-off lacquer. Used in the same manner as the previously-formedassembly, an acceptable plate from the standpoint of appearance wasproduced on the curved work surface.

A further example showing the overlap capability of this type of devicewas run utilizing a flat, highly polished sheet of copper as thesubstrate to be plated. This type of surface was used since an overlapline could more readily be seen on such surface than on a contouredsurface.

Here the wheel was made up of two sections of porous non-woven, each 1%inch thick and 4 inch in diameter. The anode was a single one-sixteenthinch thick disc, 2% inch in diameter, positioned on a inch shaft betweenthe two porous disc sections. Mounted as above and rotated at 250-300RPM on the substrate immersed in the pyrophosphate zinc bath, plate wasdeposited at amps/ft. for 1 minute. The area under the wheel was abright zinc plate which visibly tapered in thickness towards the ends ofthe wheel. The wheel was then moved so that it overlapped by one-halfinch the first plated section and the run repeated. The resultingdeposit showed no overlap lines. The same experiment was repeated with aWatts nickel bath and under the same conditions as above, no overlapline was detectable. in all instances described above, the porousnon-woven was of the type illustrated in U.S. Pat. No. 3,020,139 to J.C. Mueller and the spaced non-conductive particles bonded thereon wereflint grains of about 220 grit size.

As illustrated immediately above, it is necessary where the rotativedevice of the present invention covers only a portion of the contouredsurface to be plated to provide a variation in current density over thesurface under the device. Where the single device covers the entiresurface to be plated, this necessity does not exist and the currentdensity is preferably maintained substantially uniform over the entiresurface, i.e., the anode will conform to the contour in the outersurface of the rotative device and will be maintained at substantiallyequal distances from such outer surface over the entire length oftherotative device. Where a second device is to be used to applyadditional plate adjacent to an area covered by a first device, it isthen necessary to so dispose the interior anode within each device as toprovide a current density gradient at the ends of the rotative device,or at least at the end of each where the overlap is to occur. This isgenerally done by increasing the distance from the anode to theworkpiece at such ends. Preferably the distance is such that the porousparticle-carrying media covers all of the plate deposited with suchplate tapering down from the relatively uniform thickness common to thecentral portion of the area covered by the device to zero thickness atthe ends of the device. This is not always practical and the controllingfactor is that any plate which does extend beyond the edge of therotative device must be unburnt. If this criteria is met, the plate willinherently taper and will provide a smooth juncture with such plate laiddown by the adjacent rotative device as to minimize any apparent partingor demarcation line between the adjacent plating zones. Determination ofthe arrangement of the internal anode to accomplish this is essentiallyempirical since a wide variety of variables enter into the platedeposition. As a guide to accomplish this arrangement, a conventionalHull cell may be used. This is filled with the porousparticle-supporting media to be used and with the plating solution to beused. The cell is run at the current density to be used in the actualplating and the run is continued for the time period which will beemployed for the obtaining of the desired thickness of deposit. Thedistance along the line perpendicular to the anode from the anode to theedge of the burnt area of deposit on the cell plate gives anapproximation of the correct distance of the edge of the anode in therotative device from the end of the rotative device. This is a guideonly, and the correct distance will be found empirically as stated abovefor each particular device. Oscillation of the rotative device may beemployed in some instances to help brake up any sharp line ofdemarcation between adjacent plate areas.

I claim:

1. A rotatable activating device having a complementary contoured outersurface adapted to be placed in contacting relationship with a contouredmetallic work surface to be electroplated, said outer surface comprisinga layer of a porous, flexible, compressible, non-conductivefluid-entrapping and circulating material having a plurality of spacedhard non-conductive particles secured in fixed relationship on at leastthe outer surfaceof such material; and an inert anode material sodisposed and arranged within said outer surface of said rotatableactivating device as to provide a substantially uniform current densityat the surface of at least the central portion of said contoured worksurface when said rotatable device is in contact with said.

made cathodic with respect to said inert anode.

2. A rotatable activating device as in claim 1 wherein said inert anodematerial comprises an inner shell of lesser diameter at any given pointthan that of said outer surface at the same point and is spacedsubstantially equi-distant from said outer surface over substantiallythe entire length of said rotativedevice.

3. A rotatable activating device as in claim 1 wherein said outersurface is provided by a plurality of discs of such porous, flexible,compressible, non-conductive fluid-entrapping and circulating materialmounted concentrically on a supporting shaft with the outer peripheralportions of such discs in engagement one with the other.

4. A rotatable activating device as in claim 3 wherein said inert anodematerial is provided in the form of discs concentrically mounted on saidshaft between adjacent discs of said fluid-entrapping and circulatingmaterial, said discs of anode material having a lesser diameter thansaid discs of fluid-entrapping and circulating material.

5. A rotatable activating device as in claim 1 wherein said inert anodematerial is so disposed and arranged that when said work surface is madecathodic with respect to said inert anode material, the current densityat the surface of the contoured workpiece has a gradient at at least oneend of said rotative device from said uniform current density down to acurrent density which is less than that which will produce a burntelectrodeposit on that surface of such work iec e immediately ad acentand free from contact wit said end of said rotative device.

* UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,706,650 Dated December 19, 1972 Inventors Steve Eisner It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 4 line 38, change "5.65 x 20' to read -5.65 x 1o- Col. 8, lineafter the word "much" insert -as-.

Col. 9 line 26, change (1-1/4- 1. inch)" to read 1-1 4 inch)-.

Col. 1]., line 18, change the word "brake" to -break-.

Signed and sealed this 26th day of March 19m.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PO-105O (10-69) USCOMM-DC 60376-P69 U.5. GOVERNMENT PRINTING OFFICE I969 0-366-334 Disclaimer 3,706,650.-Steve E 21mm",Schenectady, NY. CONTOUR ACTIVATING DE- VICE. Patent dated Dec. 19,1972. Disclaimer filed May 26, 1972, by the assignee, N 07t07L Company.Hereby disclaims the portion of the term of the patent subsequent toNov. 9, 1988.

[Ofiioz'al Gazette September 11 1.973.]

1. A rotatable activating device having a complementary contoured outersurface adapted to be placed in contacting relationship with a contouredmetallic work surface to be electroplated, said outer surface comprisinga layer of a porous, flexible, compressible, non-conductivefluid-entrapping and circulating material having a plurality of spacedhard nonconductive particles secured in fixed relationship on at leastthe outer surface of such material; and an inert anode material sodisposed and arranged within said outer surface of said rotatableactivating device as to provide a substantially uniform current densityat the surface of at least the central portion of said contoured worksurface when said rotatable device is in contact with said contouredwork surface and when said work surface is made cathodic with respect tosaid inert anode.
 2. A rotatable activating device as in claim 1 whereinsaid inert anode material comprises an inner shell of lesser diameter atany given point than that of said outer surface at the same point and isspaced substantially equi-distant from said outer surface oversubstantially the entire length of said rotative device.
 3. A rotatableactivating device as in claim 1 wherein said outer surface is providedby a plurality of discs of such porous, flexible, compressible,non-conductive fluid-entrapping and circulating material mountedconcentrically on a supporting shaft with the outer peripheral portionsof such discs in engagement one with the other.
 4. A rotatableactivating device as in claim 3 wherein said inert anode material isprovided in the form of discs concentrically mounted on said shaftbetween adjacent discs of said fluid-entrapping and circulatingmaterial, said discs of anode material having a lesser diameter thansaid discs of fluid-entrapping and circulating material.
 5. A rotatableactivating device as in claim 1 wherein said inert anode material is sodisposed and arranged that when said work surface is made cathodic withrespect to said inert anode material, the current density at the surfaceof the contoured workpiece has a gradient at at least one end of saidrotative device from said uniform current density down to a currentdensity which is less than that which will produce a burntelectrodeposit on that surface of such workpiece immediately adjacentand free from contact with said end of said rotative device.